This invention relates to an aircraft toilet drain assembly for use with toilet systems of the type including a holding tank for storing toilet waste and a waste valve for releasing the waste down an outlet tube, wherein a removable drain plug is installed in the outlet tube to trap any leakage of the tank contents past the waste valve which may occur during flight.
In the operation of passenger aircraft provided with flush toilet facilities, it is common to store the waste toilet products in a toilet holding tank during flight with the tank being emptied during subsequent after-flight servicing. The aircraft holding tank is customarily provided with an outlet tube which terminates in a drain nipple mounted adjacent an access opening in the aircraft fuselage, the access opening being covered by an access panel which is closed during flight. Emptying of the contents of the holding tank through the outlet tube is controlled by a waste valve mounted in the tank at the junction to the outlet tube. Because the waste valve may sometimes permit some leakage of the contents of the tank into the outlet tube during flight it has become conventional practice to install an expandable drain plug at the down stream end of the outlet tube to trap any such leakage. A cover is usually secured to the end of the nipple, downstream of the drain plug. During after flight servicing, the operator of a ground cart for emptying the aircraft toilets will remove the cover and connect one leg of a Y drain coupling tool to the drain nipple and engage the drain plug with a setting tool which can be manipulated to release the drain plug from its expanded condition and withdraw the plug from the nipple. After that, the waste valve is opened permitting the tank contents to flow out through a second leg of the Y-drain coupling, which branches from the first leg and directs the contents into the ground cart. Such a system is disclosed in U.S. Pat. No. 3,010,694 to William B. Lynch, assigned to the same assignee as the present application. In addition, reference may also be made to co-pending application Ser. No. 691,562, filed June 1, 1976, of William J. Killam for "Aircraft Toilet Drain Plug" also assigned to the assignee of the present application.
Although the system disclosed in the Lynch U.S. Pat. No. 3,010,694 has proved highly successful, problems can arise if a forgetful or lazy ground cart operator fails to re-install a drain plug which he removed for after-flight servicing, prior to the next flight. For example, such an operator may leave the removed drain plug on the setting tool of the Y-drain coupling and forget to replace it in the outlet tube. When he commences to service the next aircraft, he will find that his setting tool cannot be engaged with the drain plug at which point he will discover the presence of the drain plug left behind from the previous aircraft. Because the existence of a surplus drain plug is a tell-tale that the preceding aircraft has been improperly cleared for flight without a drain plug, which is a violation of operating procedures for which penalties can be imposed by airport and airline authorities, a ground cart operator having a surplus drain plug will often try to conceal the fact by disposing of it in the trash. This is not an infrequent or minor problem, some airlines are presently suffering losses of drain plugs, primarily due to this cause, costing thousands of dollars annually.
In addition to the foregoing plug loss problem, safety and health problems can also arise with respect to any aircraft that has been improperly returned to the flight line without an installed drain plug. If there is leakage of a significant quantity of waste down the outlet tube during flight, the outlet cover is unlikely to provide a sufficiently substantial seal to prevent escape of toilet fluids to the exterior of the fuselage and such escaped toilet fluids can cause corrosion problems and even more serious potential aircraft safety problems. Even if the leakage is insufficient to displace the cover, but merely accumulates upstream of it, the presence of an accumulated head of waste in the outlet tube can be extremely upleasant for the unsuspecting ground cart operator at the next airport when he removes the drain nipple cover during after-flight servicing.